Electrical equipment, both stationary and portable, almost invariably requires a number of electrical connections. Such connections are between control elements, e.g., switches, printed circuit boards and the like, and wiring used to carry electrical power between the elements themselves and/or between the elements and controlled components such as an electric drive motor.
And, often, the number of connections suggests using a strip-like, multi-connection device called a terminal block. Such a block "gangs" the connections and provides a more convenient central location for them. An example of a strip-like connector for flat cable is shown in U.S. Pat. No. 4,367,006 (Rehbogen, Jr. et al.) and other examples are shown in the product literature of Wago Corporation.
A common way to effect electrical connections without the use of solder involves wire nuts, compression lugs affixed by screws or other types of threaded devices. Another way to make an electrical connection is to solder a wire to a terminal in the manner depicted in U.S. Pat. No. 2,503,559 (Miloche). Still other types of electrical connectors are of the "push-in" type and involve spring-like devices to contact wire inserted into them. Examples of connectors of this latter type are shown in U.S. Pat. Nos. 4,036,545 (Mysiak et al.) and 4,673,232 (Kubota et al.) and in the aforementioned Wago literature.
While prior art connectors and terminal blocks have been generally satisfactory for their intended purposes, they are attended by certain disadvantages. One disadvantage arises from differences in the demands of the application.
Manufacturers of capital-goods equipment built in relatively small quantities (material handling cranes, for example) and used for many hours each day can usually afford the labor and material costs which attend the use of threaded connectors. Such costs are a relatively small part of the overall machine cost. And, often, the higher equipment power levels and the sometimes-abusive use experienced by such equipment dictate larger wire and threaded connectors to help assure long-lived, trouble-free connections.
As a contrasting example, small appliances (especially those intended for the home) are used relatively infrequently and then only for short durations. And their power requirements are modest. Such appliances are typically sold in highly price-competitive markets and a cost reduction of a few cents per appliance is very attractive to the appliance manufacturer.
Although small appliances impose quite different demands upon the machine electrical system and upon the techniques used during initial assembly, designers of connecting devices used therein have not fully appreciated how to best address such demands. For example, threaded and "twist-on" connectors are still find use in such appliances for connecting wires together. Such connectors are "labor-intensive"--the time required to use them in assembling the product is quite significant.
And while terminal blocks are used in small appliances, they are often mounted to the appliance housing using separate fasteners. Such fasteners are commonly installed by hand or with hand tools on an assembly line and the appliance is thereby additionally "burdened" with an incremental labor cost which, in view of the invention, is unnecessary.
Another disadvantage of certain known terminal blocks is that they are devoid of any feature which helps avoid damage to the electrical connector by improperly "tugging" on the wire attached to such connector. U.S. Pat. No. 4,036,545 (Mysiak et al.) is an example of such a terminal block. After the wire is connected, tugging it toward one or the other of the terminal wall portions might impair the integrity of such terminal.